Hibernate loading a lazy proxy, but I only need the PK

Question

I have these entities:

@Entity
public class Room {

    @ManyToOne(optional=true,fetch=FetchType.LAZY)
    private Player player1;

    ...

}

@Entity
public class Player {

    @Id
    @Column(updatable=false)
    private long id;

    public long getId() {
        return id;
    }

    ...

}

Now, this statement inside Room...

player1.getId();

...will cause that entire Player entity to be fetched from the database. However, I just need its primary key, id, which it should already have (otherwise how can it fetch the data?).

How can I access the lazy Player proxy's id without triggering database access?

Answer 1

Hibernate should keep the object's ids linked also to the current Session. And there is a getIdentifier() method on the Session that should get the id. The documentation is not saying anything about it, but normally it shouldn't initialize the object.

Answer 2

You could have a attribute of @Column private long playerId on the Room entity. You could call this attribute to get the id without having to call the entire Player object in the transaction.

This would only work if the playerId was also stored in the Room entity table (or view etc), but I assume it must be as it's needed to be able to make the join in the first place.

edit : as @Adam Dyga mentioned below, these should be insertable and updatable both as false

@Entity
public class Room {

    @ManyToOne(optional=true,fetch=FetchType.LAZY)
    private Player player1;
    @Column(name="id", insertable = false, updatable = false) 
    private long playerId
    ...

}